Sensor assembly

ABSTRACT

A system with a sensor assembly is used to determine direction of movement of an object so that accuracy of position calculation is improved. The sensor assembly measures at least two operational characteristics and generates corresponding operational characteristic signals. A control unit monitors and compares transitions of the signals to more accurately determine direction of movement for the object.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The application claims priority to U.S. Provisional ApplicationNo. 60/328,439, which was filed on Oct. 9, 2001.

BACKGROUND OF THE INVENTION

[0002] This invention relates to a system that monitors two sensorsignals to determine direction of movement of an object so that positionof the object can be more accurately determined.

[0003] Many different types of control systems monitor variouscharacteristics of an object in order to make control decisions. Forexample, sensors can monitor and generate data that can be used todetermine speed, position, and/or direction of movement of the object.Direction is determined by comparing two sensor signals to each otherand position is incremented or decremented according to the direction. Asystem micro controller calculates position. It is important that adetermination of direction of movement be accurate so that position canbe accurately determined. Misjudgments of the direction can result inerror in position calculation.

[0004] Misjudgments can occur either by a signal phase shift or bynoise. The phase shift is caused by imbalance between the two sensorsand/or imbalance between the interface circuits for the sensors. Noisecan also cause misjudgments. For example, if the first sensor turns highfrom low due to noise when a rising edge of the second sensor isreceived, the direction of movement can be misjudged.

[0005] Thus, it is desirable to have a system that can more accuratelydetermine direction of movement of an object to increase accuracy ofposition determination.

SUMMARY OF THE INVENTION

[0006] In general terms, this invention monitors signal transitions toverify whether or not direction of movement of a moving object has beenaccurately determined to improve the accuracy of position calculation.

[0007] An example method and system designed according to this inventionincludes a sensor assembly that measures at least two operationalcharacteristics. The sensor assembly generates first and secondoperational characteristic signals. A control unit compares transitionsof the signals and the direction of movement is determined based onthese transitions. The signals are continuously monitored over time todetermine changes in direction of movement. First direction is checked.If a new direction is indicated, which is different than the previousdirection, current speed is compared to a threshold speed. If thecurrent speed exceeds the threshold speed then the new direction isdiscarded as inaccurate data.

[0008] Optionally, first check speed and any changes in speed. If thespeed is more than a threshold speed or increasing then there is no needto check direction as the same direction is assumed.

[0009] The subject system and method reduces data misinterpretationscaused by noise or intermittent phase shifts between a pair ofoperational characteristic signals to produce a more accurate directiondetermination, which in turn provides increased accuracy in positioncalculation. These and other features of the present invention can bebest understood from the following specifications and drawings, thefollowing of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 schematically illustrates a vehicle having moveable panelsthat are controlled by a system designed according to this invention.

[0011]FIG. 2 schematically illustrates a sensor and control systemincorporating the subject invention.

[0012]FIG. 3 is a Signal Level vs. Time graph for a pair of sensorsoperating correctly.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0013] While the subject invention can be used in any of various typesof control systems to improve accuracy of position calculation of amoving object, the following description uses vehicle door closuresystems as an example. FIG. 1 schematically illustrates a vehicle 20having a moveable door panel 22 and a moveable lift gate 24. The vehicle20 is provided with a system designed according to this invention forautomatically moving the door 22 or lift gate 24 with a power closurearrangement that operates as generally known in the art.

[0014] The illustrated example vehicle includes a switch 26 supportedwithin a vehicle for selectively activating the power closure system toclose the door 22 or lift gate 24. The illustrated example also includesa remote signaling device 28 such as a key fob having at least oneswitch 30 that an individual can use to selectively activate the powerclosure system.

[0015] Any system such as power window, wheel sensor for ABS, andsteering wheel sensor, which uses a pair of “relative” sensors todetermine speed, position, and direction, can incorporate features ofthe subject invention.

[0016]FIG. 2 shows a schematic illustration of a “relative” sensor andcontrol assembly 32 that is used to determine vehicle door speed,position, and direction for the door 22 or lift gate 24 as the door 22or lift gate 24 moves between open and closed positions. Examples of the“relative” sensor are encoder and Hall Effect sensors. These sensorsinclude a pair of sensors 34, 38, which read either an optical (in caseof encoder) or a magnetic (in case of Hall Effect sensor) signal fromthe same ring. The output of the sensors 34, 38 is square wave as shownin FIG. 3, whose frequency changes proportionally to the rotationalspeed of the ring. The two sensors 34, 38 essentially output the samesignal 36, 40 because both read the same ring, but output at a slightlydifferent timing because they are placed separately. Thus one signal 36leads the other signal 40 in one direction and follows in the otherdirection as shown in FIG. 3. This is how the direction is determined aswill be explained in greater detail below.

[0017] It should be understood that the sensors 34, 38 could be any typeof contact or non-contact sensors known in the art. Further, while thesensors 34, 38 are shown as separate sensors, it should be understoodthat a single sensor assembly could also be used to generate both thefirst signal 36 and the second signal 40. Finally, while a door closuresystem is shown in FIG. 1, it should be understood that the sensors 34,38 could be associated with any type of object 46 including, but notlimited to, a vehicle wheel, steering wheel, and power window.

[0018] Direction is determined by comparing the two sensor signals toeach other and position is incremented or decremented according to thedirection. A system micro controller calculates position. It isimportant that a determination of direction of movement be accurate sothat position can be accurately determined. Misjudgments of thedirection can result in error in position calculation. Misjudgments canoccur either by a signal phase shift or by noise.

[0019] For example, the order of sensor S1 and S2 might be opposite,causing misjudgment of direction. The phase shift is caused by imbalancebetween the two sensors S1 and S2 and the interface circuits the sensorsS1 and S2 thus gets worse as its frequency gets higher.

[0020] Misjudgment can also be a result of noise. For example, if onesensor S1 turns high from low due to noise when rising edge of the othersensor S2 is received, the direction is misjudged as open.

[0021] The signals 36, 40 are transmitted to a control unit 42 withmemory 44 that calculates the speed, the direction, and the position ofthe door 22 or lift gate 24 by comparing the data from the signals 36,40. It should be understood that any type of control unit 42 known inthe art could be used including a central processing unit, amicroprocessor, or other similar device.

[0022] The control unit 42 continuously monitors and compares thesignals 36, 40 and their respective transitions as the door 22 or liftgate 24 moves between open and closed positions. For every transition ofone sensor 34, either rising or falling, the other sensor 38 willtransition before the first sensor 34 transitions again. In other words,if one signal 36 transitions, as indicated at t1 in FIG. 3, the othersignal 40 will also correspondingly transition, as indicated at t2, andwill do so prior to the first signal 36 being able to make a subsequenttransition, as shown at t3. If the sensor assembly is operatingcorrectly, the signals 36, 40 will track each other as shown in FIG. 3.

[0023] As FIG. 3 shows, direction is judged in the following way. For asituation where a rising edge of sensor S2 is received by the controlunit 42 there are generally two possibilities. If sensor S1 is low, thensensor S2 is leading thus the door is closing, or if sensor S1 is high,then sensor S2 is following thus the door is opening. It should beunderstood that the opposite orientation could also be used, i.e. ifsensor S1 is low then sensor S2 is leading thus the door is opening,while if sensor S1 is high, then sensor S2 is following thus the door isclosing.

[0024] For a situation where a falling edge of sensor S2 is received bythe control unit 42 there are also generally two possibilities. Ifsensor S1 is low, then sensor S2 is following thus the door is opening,or if sensor S1 is high, then sensor S2 is leading thus the door isclosing. It should be understood that the opposite orientation couldalso be used, i.e. if sensor S1 is low then sensor S2 is following thusthe door is closing, while if sensor S1 is high, then sensor S2 isleading thus the door is opening.

[0025] Position is incremented or decremented depending on the directionevery time an edge (rising or falling) is detected. For example, if thedirection is judged as opening, position is incremented. If thedirection is judged as closing, then position is decremented. If thedirection is misjudged as opening, for example, when the door isactually closing, position gets incremented instead of decremented,resulting in error in position calculation.

[0026] Having the correct data is critical to determining an accuratedoor direction. If there is an intermittent phase shift between thesignals 36 and 40, the data may be misinterpreted and inaccuracies indoor direction can lead to a wrong direction fault warning or errorsignal within the system. The subject invention addresses this problemby monitoring the transitions along with door speed to determinedirection of movement to more accurately be able to determine position.

[0027] By monitoring and comparing signal transitions of the signals 36and 40, an initial direction of vehicle door movement is determined.This initial direction of vehicle door movement is stored in memory 44as a direction history. The size of the direction history can be byte,word, or any size that is sufficient for making a sound judgment. Thesystem continues to monitor and compare signal transitions of thesignals 36 and 40 to determine changes in direction of vehicle doormovement. Current door speed is compared to a threshold speed inresponse to receiving an indication of a new direction of vehicle doormovement that is different than the direction previously stored as thedirection history. If the threshold speed is exceeded then the newdirection is discarded as inaccurate data. Position is incremented ordecremented based on the direction determination discussed above.

[0028] For example, when a new direction is received, the directionhistory byte is shifted to the left and the new direction is stored as aleast significant bit (LSB) or shifted to the right and the newdirection is stored as a most significant bit (MSB). If the newdirection does not match the initial or previous direction, and the doorspeed is greater than the threshold speed, the new direction isdiscarded. The new direction is determined to be inaccurate data becausethe system cannot change the direction abruptly if it is moving greaterthan the threshold speed. Thus, if the new direction is different thanthe previous direction and the door speed is less than or equal to thethreshold speed, then the new direction is determined to be valid. Itshould be understood that the threshold speed can be any predeterminedspeed and could vary based on vehicle type and application.

[0029] The subject invention addresses these problems by using the factthat speed gradually reduces to zero and then gradually increases whenthe direction changes in combination with the following rules. Whenspeed is more than the predetermined threshold or is increasing,direction cannot change and can be assumed to be unchanged. Prior tomaking a final decision, the control unit 42 reviews the history ofdirection and if the history is consistent, i.e. all of the historyshows the same direction, then the control unit 42 decides on the samedirection without actually checking the direction. If the history is notconsistent, then the history cannot be relied on and the directionshould be checked. On the other hand, when speed is less than thepredetermined threshold and decreasing, direction may change, thus thedirection is checked.

[0030] Although a preferred embodiment of this invention has beendisclosed, a worker of ordinary skill in this art would recognize thatcertain modifications would come within the scope of this invention. Forthat reason, the following claims should be studied to determine thetrue scope and content of this invention.

1. A method for determining a direction in which an object is movingcomprising the steps of: (a) generating a first signal representing afirst operational characteristic; (b) generating a second signalrepresenting a second operational characteristic; (c) comparing thefirst and second signals to determine an initial direction; and (d)monitoring transitions of the first and second signals over time toverify that the initial direction is accurate.
 2. A method as set forthin claim 1 including the step of comparing an object speed to apredetermined threshold speed during step (d) to determine whether theinitial direction is accurate.
 3. A method as set forth in claim 1wherein step (c) further includes comparing transitions of the first andsecond signals over time to determine the initial direction and storingthe initial direction in memory as a direction history.
 4. A method asset forth in claim 3 further including the steps of subsequentlychecking direction to generate a new direction, comparing the newdirection to the initial direction, and checking speed if the newdirection is different than the initial direction.
 5. A method as setforth in claim 4 further including the step of discarding the newdirection if the speed is more than a predetermined threshold speed orspeed is increasing.
 6. A method as set forth in claim 1 including thesteps of measuring speed and changes in speed, comparing speed to apredetermined threshold speed, and only checking direction if the speedis less than the predetermined threshold speed.
 7. A method as set forthin claim 6 including the step of assuming no direction change if thespeed is more than the predetermined threshold speed or is increasing.8. A method as set forth in claim 1 including the steps measuring speedand changes in speed, comparing speed to a predetermined thresholdspeed, and only checking direction if the speed is decreasing.
 9. Amethod as set forth in claim 1 including the steps of measuring speedand changes in speed, comparing speed to a predetermined thresholdspeed, and only checking direction if the speed is decreasing and isless than the predetermined threshold speed.
 10. A method as set forthin claim 1 wherein the moving object comprises a door panel.
 11. Amethod as set forth in claim 1 wherein the moving object comprises apower window.
 12. A method as set forth in claim 1 wherein the movingobject comprises a vehicle wheel.
 13. A method as set forth in claim 1wherein the moving object comprises a steering wheel.
 14. A system forverifying direction of movement of an object in response to anintermittent sensor phase shift comprising: a sensor assembly formeasuring at least first and second object operational characteristicsas said object moves to generate first and second object operationalcharacteristic signals; and a control unit for comparing signaltransitions of said first and second object operational characteristicsignals to determine an initial direction of object movement andcontinuing to compare signal transitions of said first and second objectoperational characteristic signals over time to verify accuracy ofinitial direction determination.
 15. A system as set forth in claim 14wherein said control unit subsequently checks direction to generate anew direction, compares the new direction to said initial direction,checks speed if the new direction is different than said initialdirection, and discards the new direction if the speed is more than apredetermined threshold speed.
 16. A system as set forth in claim 14wherein said control unit only checks direction if speed is less than apredetermined threshold speed.
 17. A system as set forth in claim 14wherein said control unit only checks direction if speed is decreasing.18. A system as set forth in claim 14 wherein said control unit onlychecks direction if speed is decreasing and less than a predeterminedthreshold speed.
 19. A system as set forth in claim 14 wherein saidcontrol unit assumes no direction change if speed is more than apredetermined threshold speed or is increasing.
 20. A system as setforth in claim 14 wherein said object comprises a vehicle doorcontrolled by a power closure system.
 21. A system as set forth in claim14 wherein said object comprises a steering wheel.
 22. A system as setforth in claim 14 wherein said object comprises a power window.
 23. Asystem as set forth in claim 14 wherein said object comprises a vehiclewheel and said sensor assembly comprises an ABS wheel sensor.